Caption: Ringworm fungal infection of the groin. Close-up of a tinea fungal infection on the skin of the groin of a man. Ringworm (tinea) is a disease caused by a fungal infection of the skin. It can be caused by various fungi, including Microsporum and Trichophyton. When it affects the skin of the groin, it is known as tinea cruris. Treatment is with antifungal drugs. Photographed in India.